Along with the improvement in processing capability of game devices, a number of games have come on the market wherein a player character and a non-player character are moved in a game field modeled three-dimensionally. Recently, wireless type game controllers become widely available as input devices for games. Further, a technology has been proposed, which utilizes as an input for games, not only conventional button manipulation, but also the movement of an object moved by a user in an image captured by a camera.